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 // Copyright 2009 the V8 project authors. All rights reserved.

 // Redistribution and use in source and binary forms, with or without

 // modification, are permitted provided that the following conditions are

 // met:

 //

 //     * Redistributions of source code must retain the above copyright

 //       notice, this list of conditions and the following disclaimer.

 //     * Redistributions in binary form must reproduce the above

 //       copyright notice, this list of conditions and the following

 //       disclaimer in the documentation and/or other materials provided

 //       with the distribution.

 //     * Neither the name of Google Inc. nor the names of its

 //       contributors may be used to endorse or promote products derived

 //       from this software without specific prior written permission.

 //

 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR

 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT

 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT

 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY

 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE

 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 // This benchmark is based on a JavaScript log processing module used

 // by the V8 profiler to generate execution time profiles for runs of

 // JavaScript applications, and it effectively measures how fast the

 // JavaScript engine is at allocating nodes and reclaiming the memory

 // used for old nodes. Because of the way splay trees work, the engine

 // also has to deal with a lot of changes to the large tree object

 // graph.

 var Splay = new BenchmarkSuite('Splay', 81491, [

   new Benchmark("Splay", SplayRun, SplaySetup, SplayTearDown)

 ]);

 // Configuration.

 var kSplayTreeSize = 8000;

 var kSplayTreeModifications = 80;

 var kSplayTreePayloadDepth = 5;

 var splayTree = null;

 function GeneratePayloadTree(depth, tag) {

   if (depth == 0) {

     return {

       array  : [ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 ],

       string : 'String for key ' + tag + ' in leaf node'

     };

   } else {

     return {

       left:  GeneratePayloadTree(depth - 1, tag),

       right: GeneratePayloadTree(depth - 1, tag)

     };

   }

 }

 function GenerateKey() {

   // The benchmark framework guarantees that Math.random is

   // deterministic; see base.js.

   return Math.random();

 }

 function InsertNewNode() {

   // Insert new node with a unique key.

   var key;

   do {

     key = GenerateKey();

   } while (splayTree.find(key) != null);

   var payload = GeneratePayloadTree(kSplayTreePayloadDepth, String(key));

   splayTree.insert(key, payload);

   return key;

 }

 function SplaySetup() {

   splayTree = new SplayTree();

   for (var i = 0; i < kSplayTreeSize; i++) InsertNewNode();

 }

 function SplayTearDown() {

   // Allow the garbage collector to reclaim the memory

   // used by the splay tree no matter how we exit the

   // tear down function.

   var keys = splayTree.exportKeys();

   splayTree = null;

   // Verify that the splay tree has the right size.

   var length = keys.length;

   if (length != kSplayTreeSize) {

     throw new Error("Splay tree has wrong size");

   }

   // Verify that the splay tree has sorted, unique keys.

   for (var i = 0; i < length - 1; i++) {

     if (keys[i] >= keys[i + 1]) {

       throw new Error("Splay tree not sorted");

     }

   }

 }

 function SplayRun() {

   // Replace a few nodes in the splay tree.

   for (var i = 0; i < kSplayTreeModifications; i++) {

     var key = InsertNewNode();

     var greatest = splayTree.findGreatestLessThan(key);

     if (greatest == null) splayTree.remove(key);

     else splayTree.remove(greatest.key);

   }

 }

 /**

  * Constructs a Splay tree.  A splay tree is a self-balancing binary

  * search tree with the additional property that recently accessed

  * elements are quick to access again. It performs basic operations

  * such as insertion, look-up and removal in O(log(n)) amortized time.

  *

  * @constructor

  */

 function SplayTree() {

 };

 /**

  * Pointer to the root node of the tree.

  *

  * @type {SplayTree.Node}

  * @private

  */

 SplayTree.prototype.root_ = null;

 /**

  * @return {boolean} Whether the tree is empty.

  */

 SplayTree.prototype.isEmpty = function() {

   return !this.root_;

 };

 /**

  * Inserts a node into the tree with the specified key and value if

  * the tree does not already contain a node with the specified key. If

  * the value is inserted, it becomes the root of the tree.

  *

  * @param {number} key Key to insert into the tree.

  * @param {*} value Value to insert into the tree.

  */

 SplayTree.prototype.insert = function(key, value) {

   if (this.isEmpty()) {

     this.root_ = new SplayTree.Node(key, value);

     return;

   }

   // Splay on the key to move the last node on the search path for

   // the key to the root of the tree.

   this.splay_(key);

   if (this.root_.key == key) {

     return;

   }

   var node = new SplayTree.Node(key, value);

   if (key > this.root_.key) {

     node.left = this.root_;

     node.right = this.root_.right;

     this.root_.right = null;

   } else {

     node.right = this.root_;

     node.left = this.root_.left;

     this.root_.left = null;

   }

   this.root_ = node;

 };

 /**

  * Removes a node with the specified key from the tree if the tree

  * contains a node with this key. The removed node is returned. If the

  * key is not found, an exception is thrown.

  *

  * @param {number} key Key to find and remove from the tree.

  * @return {SplayTree.Node} The removed node.

  */

 SplayTree.prototype.remove = function(key) {

   if (this.isEmpty()) {

     throw Error('Key not found: ' + key);

   }

   this.splay_(key);

   if (this.root_.key != key) {

     throw Error('Key not found: ' + key);

   }

   var removed = this.root_;

   if (!this.root_.left) {

     this.root_ = this.root_.right;

   } else {

     var right = this.root_.right;

     this.root_ = this.root_.left;

     // Splay to make sure that the new root has an empty right child.

     this.splay_(key);

     // Insert the original right child as the right child of the new

     // root.

     this.root_.right = right;

   }

   return removed;

 };

 /**

  * Returns the node having the specified key or null if the tree doesn't contain

  * a node with the specified key.

  *

  * @param {number} key Key to find in the tree.

  * @return {SplayTree.Node} Node having the specified key.

  */

 SplayTree.prototype.find = function(key) {

   if (this.isEmpty()) {

     return null;

   }

   this.splay_(key);

   return this.root_.key == key ? this.root_ : null;

 };

 /**

  * @return {SplayTree.Node} Node having the maximum key value.

  */

 SplayTree.prototype.findMax = function(opt_startNode) {

   if (this.isEmpty()) {

     return null;

   }

   var current = opt_startNode || this.root_;

   while (current.right) {

     current = current.right;

   }

   return current;

 };

 /**

  * @return {SplayTree.Node} Node having the maximum key value that

  *     is less than the specified key value.

  */

 SplayTree.prototype.findGreatestLessThan = function(key) {

   if (this.isEmpty()) {

     return null;

   }

   // Splay on the key to move the node with the given key or the last

   // node on the search path to the top of the tree.

   this.splay_(key);

   // Now the result is either the root node or the greatest node in

   // the left subtree.

   if (this.root_.key < key) {

     return this.root_;

   } else if (this.root_.left) {

     return this.findMax(this.root_.left);

   } else {

     return null;

   }

 };

 /**

  * @return {Array<*>} An array containing all the keys of tree's nodes.

  */

 SplayTree.prototype.exportKeys = function() {

   var result = [];

   if (!this.isEmpty()) {

     this.root_.traverse_(function(node) { result.push(node.key); });

   }

   return result;

 };

 /**

  * Perform the splay operation for the given key. Moves the node with

  * the given key to the top of the tree.  If no node has the given

  * key, the last node on the search path is moved to the top of the

  * tree. This is the simplified top-down splaying algorithm from:

  * "Self-adjusting Binary Search Trees" by Sleator and Tarjan

  *

  * @param {number} key Key to splay the tree on.

  * @private

  */

 SplayTree.prototype.splay_ = function(key) {

   if (this.isEmpty()) {

     return;

   }

   // Create a dummy node.  The use of the dummy node is a bit

   // counter-intuitive: The right child of the dummy node will hold

   // the L tree of the algorithm.  The left child of the dummy node

   // will hold the R tree of the algorithm.  Using a dummy node, left

   // and right will always be nodes and we avoid special cases.

   var dummy, left, right;

   dummy = left = right = new SplayTree.Node(null, null);

   var current = this.root_;

   while (true) {

     if (key < current.key) {

       if (!current.left) {

         break;

       }

       if (key < current.left.key) {

         // Rotate right.

         var tmp = current.left;

         current.left = tmp.right;

         tmp.right = current;

         current = tmp;

         if (!current.left) {

           break;

         }

       }

       // Link right.

       right.left = current;

       right = current;

       current = current.left;

     } else if (key > current.key) {

       if (!current.right) {

         break;

       }

       if (key > current.right.key) {

         // Rotate left.

         var tmp = current.right;

         current.right = tmp.left;

         tmp.left = current;

         current = tmp;

         if (!current.right) {

           break;

         }

       }

       // Link left.

       left.right = current;

       left = current;

       current = current.right;

     } else {

       break;

     }

   }

   // Assemble.

   left.right = current.left;

   right.left = current.right;

   current.left = dummy.right;

   current.right = dummy.left;

   this.root_ = current;

 };

 /**

  * Constructs a Splay tree node.

  *

  * @param {number} key Key.

  * @param {*} value Value.

  */

 SplayTree.Node = function(key, value) {

   this.key = key;

   this.value = value;

 };

 /**

  * @type {SplayTree.Node}

  */

 SplayTree.Node.prototype.left = null;

 /**

  * @type {SplayTree.Node}

  */

 SplayTree.Node.prototype.right = null;

 /**

  * Performs an ordered traversal of the subtree starting at

  * this SplayTree.Node.

  *

  * @param {function(SplayTree.Node)} f Visitor function.

  * @private

  */

 SplayTree.Node.prototype.traverse_ = function(f) {

   var current = this;

   while (current) {

     var left = current.left;

     if (left) left.traverse_(f);

     f(current);

     current = current.right;

   }

 };